A new approach to testing for the presence of the virus that causes Covid-19 may lead to tests that are faster, less expensive, and potentially less prone to erroneous results than existing detection methods. Although the work, based on quantum effects, is still theoretical, these detectors could potentially be adapted to detect virtually any virus, according to the researchers.
The new approach is described in an article published in the journal Nano letters, by Changhao Li, an MIT doctoral student; Paola Cappellaro, professor of nuclear science and engineering and physics; and Rouholla Soleyman and Mohammad Kohandel from the University of Waterloo.
Existing tests for the SARS-CoV-2 virus include rapid tests that detect specific viral proteins and polymerase chain reaction (PCR) tests that take several hours to process. None of these tests can quantify the amount of virus present with great precision. Even benchmark PCR tests can have false negative rates of over 25%. In contrast, the team’s analysis shows that the new test could have false negative rates of less than 1%. The test could also be sensitive enough to detect a few hundred strands of viral RNA, in just a second.
The new approach uses atomic-scale defects in tiny pieces of diamond, known as nitrogen vacancy (NV) centers. These tiny defects are extremely sensitive to minute disturbances, thanks to the quantum effects that occur in the crystal lattice of diamond, and are explored for a wide variety of detection devices requiring high sensitivity.
The new method would involve coating the nanodiamonds containing these NV centers with a material that is magnetically coupled to them and that has been processed to bind only with the virus-specific RNA sequence. When virus RNA is present and binds to this material, it disrupts the magnetic connection and causes changes in the fluorescence of the diamond which are easily detected with a laser based optical sensor.
The sensor only uses low-cost materials (the diamonds involved are smaller than grains of dust) and the devices could be scaled up to analyze a whole batch of samples at once, the researchers said. The gadolinium-based coating with its organic molecules adapted to RNA can be produced using common chemical processes and materials, and the lasers used to read the results are comparable to cheap and widely available commercial green laser pointers. .
While this initial work was based on detailed mathematical simulations that proved that the system can work in principle, the team continues to work on translating it into a working laboratory-scale device to confirm the predictions.
We don’t know how long it will take to do the final demo. “
Changhao Li, PhD student, Massachusetts Institute of Technology
Their plan is to do a basic proof-of-principle lab test first, and then work on ways to optimize the system to run on real virus diagnostic applications.
The multidisciplinary process requires a combination of expertise in quantum physics and engineering, to produce the detectors themselves, and in chemistry and biology, to develop the molecules that bind to viral RNA and to find ways to bind them. to diamond surfaces.
Even though complications arise when translating the theoretical analysis into a working device, says Cappellaro, there is such a margin of false negatives predicted from this work that it will likely still have a strong advantage over PCR tests. standard in this regard. And even if the precision were the same, this method would still have the major benefit of producing its results in a matter of minutes, rather than taking several hours, she says.
The basic method can be adapted for any virus, she says, including any new virus that might emerge, simply by tailoring the compounds that are attached to the nanodiamond sensors to match the generic material of the virus. specific target.
He adds that for his company, “We are very excited to use diamond-based quantum sensors to create powerful biomedical diagnostic tools. Needless to say, we will follow with great interest the translation of the ideas presented in this work in the lab.